Support is requested for the 1991 Gordon Research Conference on Mammalian DNA Repair--a biannual conference which brings together a diverse group of scientists interested in the extent to which damaged DNA is repaired in mammalian cells, the mechanism by which this repair is brought about and the consequences of incomplete and inaccurate repair. This topic not only is of particular importance in assessment of the risk associated with exposure to environmental mutagenic and carcinogenic hazards but also is of much interest in many other disparate areas such as the variations among individuals of the efficacy of chemotherapeutic agents and in theories of aging. The conference provides the opportunity for the interaction, in a relatively informal setting, of a group of scientists who often do not find themselves at the same meeting. Discussions between the participants are likely to lead to an exchange of ideas, techniques and approaches which will benefit many different research projects and areas. This year's meeting will include nine sessions covering a range of areas in which progress is being made rapidly and will feature talks by leaders in the fields aimed not only at scientists in the immediate area but those in related disciplines. The sessions will cover DNA damage caused by a variety of environmental agents including ultraviolet light, irradiation, oxidation and chemicals. There will be an emphasis on molecular, and genetic and biochemical approaches leading to insights into fundamental mechanisms. Sessions will cover: the specificity of DNA repair in terms both of DNA conformation, the structure of adducts and the differential susceptibility of various sites within the genome; the purification and cloning of DNA repair proteins and the use of cDNA and genomic probes as well as monospecific antisera towards them to study the regulation of DNA repair; the study of heritable diseases involving defects in DNA repair; the importance of DNA damage persistence and repair in determination of susceptibility to environmental carcinogenic and mutagenic agents; and the study of repair and mutagenesis by use of DNA or oligonucleotides containing defined lesions. Support is requested towards the travel and conference fees for key participants who otherwise would be unable to attend.